ABSTRACT Indoor tanning is a major preventable risk factor for melanoma, the deadly form of skin cancer and now the #1 cancer in women ages 25-29. The Surgeon General's 2014 Call to Action to Prevent Skin Cancer emphasizes the need to reduce indoor tanning by developing and disseminating tailored messages to high-risk populations. Social media may be a powerful means to reach tanners given tanners are young adults and use social media at higher rates than nontanners. Although social media have the capacity to reach users with health messaging, not all users are persuaded by health messages. Recent work has revealed that tanners are aware that tanning increases risk for skin cancer. For many, the immediate benefits of tanning (e.g., physical appearance) override concerns about long-term consequences (e.g., cancer). Messages that increase the salience of the immediate negative consequences of indoor tanning might be more effective at changing behavior. We content-analyzed 1000 tweets about indoor tanning and discovered that 31% of tweets by tanners described negative experiences at the tanning salon (e.g., painful burns, deceptive salon practices, unsanitary conditions, peeping Toms). Frequent exposure to peer reports of negative experiences might shift perceptions about the desirability of tanning. Tweets are brief, narratives about everyday experiences and thus may be useful in behavioral interventions. Transportation theory suggests that when people identify with characters in a story, beliefs, attitudes, and behavior can be affected. We propose to develop a social media intervention that is comprised of peer-generated social media content about 1) negative experiences with indoor tanning, 2) positive reactions to quitting tanning, and 3) positive experiences using tanning alternatives. To inform the intervention, we will extract and content analyze tanners' tweets about their experiences to identify narrative content for the intervention. We will use social marketing theory and a user-centered design approach to develop a social media feed that tanners find interesting and persuasive. We plan to connect to audience values by embedding the intervention in a feed based on a topic that tanners tell us they value (e.g., beauty). Intervention messages about indoor tanning will be peppered throughout but presented in a way that is relevant to the theme topic. To identify topics of high interest to tanners we will content analyze topics they share on social media and then conduct focus groups of tanners to provide deeper perspective, pre-test intervention messages, and obtain consensus on the feed moderator persona (e.g., peer), an engagement strategy, and preferred social network platform (e.g., Instagram, Facebook) for the intervention. Finally, we will conduct a pilot feasibility trial to evaluate an 8-week social media-delivered intervention relative to a similar feed with no tanning related content. We will conduct a preliminary test of transportation theory by examining the intervention's effect on persuasive impact and beliefs about the desirability of indoor tanning. This work will inform a randomized trial testing the efficacy of this intervention on tanning and message dissemination.